sears engine analyzer

[artron9]

Still trying to connect my old Sears Engine Analyzer to my 6volt  positive ground 52 Ford. I have tried many of the combinations various members have suggested but cannot get a proper dwell reading. I have used an external 12volt battery and have grounded the ext battery pos. to the chassis. Both leads from the analyzer have gone to the same polarity connections on the ext battery. The green coil wire I have tried on then the minus side of the coil and the positive side. Minus side is more accurate. However, I cannot get near the proper dwell reading between 58-62 degrees. The needle stays down near zero. Most people say forget it but I really want this to work. The rpm readings are accurate. The instruments available today are either too expensive or too cheap. In its day this analyzer was a great tool for tuneups. Have any thoughts?

[Bloo]

My gut feeling is it wont work, at all, ever. I hope I am wrong. My first dwellmeter was a Sears engine analyzer, a LONG time ago. It was a lunchbox-like thing about the size of a car battery. Is that what you have?

 

If so, RPM works because it is an inductive pickup that you clip around a spark plug wire. The analyzer doesn't know or care what kind of electrical system, it just sees a spark.

 

Inductive timing lights work for the same reason (if you hook them to a 12v battery for power, most wont run on 6v).

 

Dwellmeters have to connect to the switched side of the coil. That is probably the positive coil terminal on a positive ground car. It is ALWAYS the wire that goes to the points and condenser in the distributor. That is the only wire that has a dwell signal on it.

 

That wire is "hot" when the points are open (ground on a positive ground car), and "grounded" (positive on a positive ground car). If you think about it that is the same as "on" and "off". If you were to connect a testlight, the kind with a little bulb in it, to that terminal and chassis, it would flash when you crank the engine. All a dwellmeter does is compare on-time to off-time. For example, a 6 cylinder scale is 0-60 degrees. 30 degrees on a 6 cylinder scale is 50% on-time and 50% off-time.

 

If your Sears is like mine I don't really see any way it could work. It wanted to be connected to both negative and positive all the time, plus the dwell wire. If you connected it to the battery (positive to positive, negative to negative, because the opposite way would probably damage the internal electronics), the analyzer would expect the voltage to go off with points closed rather than on. Assuming 6 volts was enough to swing full scale (and it might not), it would be more or less accurate at 50% (half scale) but the scale would be backwards.

 

Hooking the spare 12v battery positive to chassis would power the unit ok, but it would still need to see the voltage go off with closed points, and it won''t. I don't see any way to get a useful signal from that.

 

You might get lucky using an old 2-wire dwellmeter hooked up backwards (ground wire to coil, dwell wire to chassis) IF (and only if) 6v happened to be enough to swing full scale. One with a manual zero knob would be the best bet.

 

I bought a 6v used dwellmeter and repaired it. They don't come up often. I think in my Sears analyzer days I had to use a feeler gauge on 6 volt cars.

 

Edited June 19, 2019 by Bloo (see edit history)

[artron9]

Thank you for the great report! You are extremely experienced. I appreciate the  time spent relaying this information. I believe you are correct.It does make perfect sense to me . Thanks again for your meaningful assessment.